A new porphyrin meso-5,10,15,20-tetrakis[3,4-bis(carboxymethyleneoxy- phenyl]porphyrin (T3,4BCPP) was synthesised and efficiently labeled with Tc-99m. On injecting this Tc-99m labeled porphyrin to abdominal Sarcoma 120 bearing Swiss mice it accumulated in the abdominal tumour. This radiolabeled complex can thus be used for tumour detection and diagnosis.